Reinforcement of glass substrates in flexible devices

ABSTRACT

A reinforcement technique used in the fabrication of displays, such as organic light emissive diode (OLED) display, is disclosed. A stiff reinforcement lid is mounted on a thin substrate to encapsulate the OLED cells. The lid serves to reinforce the thin flexible substrate and protect it from breakage. It comprises preferably of metal or other materials that have higher stiffness and ductility than the thin substrate. The fabricated display is compatible for integration into chip cards and other flexible applications.

FIELD OF THE INVENTION

[0001] The present invention relates to displays, such as organic lightemitting diode (OLED) displays. More particularly, the invention relatesOLED displays, which are compatible for integration in chip cards orother thin flexible applications.

BACKGROUND OF THE INVENTION

[0002]FIG. 1 shows a conventional OLED device 100. The OLED devicecomprises one or more organic functional layers 110 between first andsecond electrodes 105 and 115 formed on a substrate 101. The electrodescan be patterned to form, for example, a plurality of OLED cells tocreate a pixelated OLED device. Bond pads 150, which are coupled to thefirst and second electrodes, are provided to enable electricalconnections to the OLED cells. A cap 160 is formed over the substrate toencapsulate the device, protecting the OLED cells from the environmentsuch as moisture and/or air.

[0003] The substrate is preferably made from glass due to its goodbarrier properties against moisture or air. Glass substrates provideother advantages including a smooth surface, temperature and dimensionalstability as well as availability of raw materials and processes.

[0004] For flexible applications, such as chip cards, the overall devicethickness of the devices need to be less than about 0.6 mm. As such,conventional OLEDs are incompatible since they are too thick and aretypically more than 2 mm thick. To reduce the overall thickness andimpart mechanical flexibility, thin or ultra thin glass substrateshaving a thickness of less than 0.4 mm are used. However, the thin glasssubstrates are fragile and susceptible to breakage due to mechanicalstress, such as bending of the chip card.

[0005] As evidenced from the above discussion, it is desirable toprovide a thin flexible device formed of a thin glass substrate that isnot susceptible to breakage.

SUMMARY OF THE INVENTION

[0006] The invention relates generally to OLED devices. In particular,the invention relates to the reinforcement and stabilization of displaysespecially OLED devices on ultra thin substrates, integrated into chipcards and other flexible applications.

[0007] In accordance with the invention, a reinforcement technique isprovided for flexible displays. In one embodiment of the invention, astiff and ductile cover lid is mounted on an ultra thin flexible glasssubstrate containing OLED devices. The cover lid comprises preferably ofmetal, or other materials that have higher stiffness and ductility thanthe substrate to protect it from breakage. The lid and substrate aresealed to encapsulate the OLED devices and protect them fromenvironmental and mechanical damage.

[0008] The thickness of the fabricated OLED display is less than 0.6 mm.It is suitable for integration into chip cards or other thin flexibleapplications. The reinforcement protects the ultra thin substrates frombreakage and does not affect the flexibility of the substrate. Theprocess is suitable for large area, cost effective mass production.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009]FIG. 1 shows a conventional OLED device; and

[0010]FIG. 2 shows one embodiment of the invention integrated into achip card.

[0011]FIG. 3(a) shows the result of bending a smart card containing aconventional display without metal reinforcement.

[0012]FIG. 3(b) shows the result of bending a chip card containing adisplay with metal reinforcement, according to one embodiment of theinvention.

[0013]FIG. 4 shows one embodiment of the invention.

[0014] FIGS. 5-7 show other embodiments of the invention.

PREFERRED EMBODIMENTS OF THE INVENTION

[0015] The invention relates generally to flexible devices formed onthin substrates. In one embodiment of the invention, a flexible OLEDdevice is formed on a thin glass substrate. In one embodiment of theinvention, a stiff and ductile metal cover is mounted on the substrateto reinforce it and prevent it from breaking. The OLED device isparticularly useful in thin flexible surfaces, for example, chip cards.

[0016]FIG. 2 shows a fabricated display 400, according to one embodimentof the invention, integrated into a flexible chip card 300. Typically,the chip card has outer dimensions of 86 mm by 54 mm with a thickness of0.7 mm. For a seven-segment display, for example, the OLED displaytypically occupies an area of 22 mm by 10 mm. Since the display occupiesa small fraction of the entire chip card area, the bending motionapplied during a bending test can be restricted to the region notoccupied by the display. Hence, the non-display area absorbs themechanical strain introduced to the card during bending, as shown inFIG. 3(b), and the display remains undamaged. FIG. 3(a) shows the shapeof the card that contains a display not reinforced by metal. Withoutprotection from the metal cover, the display will be subjected tomechanical strain that may cause breakage.

[0017]FIG. 4 shows one embodiment of the invention. A thin or ultra thinglass substrate 410 is provided. The glass substrate, for example, canbe made from silicate glass such as borosilicate glass. Othertransparent materials, such as sodalime glass or other types of glass,are also useful. Typically, the thickness of the thin glass substrate isless than about 0.4 mm, preferably about 0.01-0.2 mm, and morepreferably about 0.03-0.2 mm.

[0018] A conductive layer 420 is deposited on the substrate. Theconductive layer is then patterned, selectively removing portionsthereof as desired. The patterned conductive layer serves as firstelectrodes for the OLED cells.

[0019] In a preferred embodiment, a dielectric layer 470 is deposited onthe substrate after the conductive layer is patterned. The dielectriclayer, in one embodiment, comprises a photosensitive layer, such asphotosensitive resist or polyimide. Other types of photosensitive layersare also useful. The thickness of the layer is typically less than 0.5mm. The dielectric layer is patterned to form isolation pillars on thesubstrate, isolating the cathode materials. These pillars also supportthe layers above it and improve the flexibility of the device by about10 to 30 percent.

[0020] If a resist is used, the resist is patterned by selectivelyexposing it to radiation through a mask and developing it to remove theexposed or unexposed portions, depending on whether a positive ornegative active resist is used. If a non-photosensitive layer is used, aresist layer is deposited and patterned to serve as an etch mask forpatterning the non-photosensitive layer using, for example, ananisotropic etch such as a reactive ion etch (RIE).

[0021] One or more organic functional layers 460 are formed on thesubstrate, covering the conductive layer. In one embodiment, thefunctional organic layers comprise a conjugated polymer or a lowmolecular material such as Alq₃. Other types of functional organiclayers are also useful. Typically, the thickness of the organic layersis about 2-200 nm. The organic layer is then patterned, removingportions thereof to expose the anode for bond pad connections.

[0022] A second conductive layer 440 is deposited over the substrate toserve as the cathode. The second conductive layer comprises a conductivematerial such as Ca, Mg, Ba, Ag or a mixture thereof. The top electrodestrips are typically orthogonal to the bottom electrode strips. Formingtop electrode strips that are diagonal to the bottom electrode strips isalso useful. The intersections of the top and bottom electrode stripsform organic LED pixels.

[0023] A flat lid 450 is mounted on the substrate to encapsulate thedevice according to one embodiment. The lid layer comprises preferablyof metal (e.g. stainless steel alloy, aluminium alloy). Typically, thethickness of the lid layer 0.04-0.4 mm. The lid should have higherstiffness and ductility than the substrate, and good resistance againstoxidation and chemicals. The thickness of the lid and substrate stack ispreferably less than 0.6 mm so that it can be easily integrated into thechip card.

[0024] Various techniques can be used attach the lid to the substrate.In one embodiment, an adhesive 430 is used to mount the lid layer.Adhesives such as self-hardening adhesives, UV or thermal curableadhesives, or hot melt adhesives are useful. Other techniques thatemploy low temperature solder materials, ultrasonic bonding, or weldingtechniques using inductance or laser welding are also useful.

[0025] In another embodiment shown in FIG. 5, a stamped metal lid 510containing a cavity 530 can be used to encapsulate the device. Thecavity can accommodate some desiccant material 520 (e.g. getter orscavenger) to absorb residual moisture and oxygen. Alternatively, thecover lid can extend the actual outer dimensions of the substrate tofacilitate integration of the display into the chip card by mechanicalinterlocking. The metal lid can be shaped (e.g. rounded, flat orwedge-shaped) to avoid high stress at the edge of the display. Referringto FIG. 6a, a wedge-shaped metal lid 610 is used to encapsulate thedevice. The fabricated device 600 is integrated into the flexible chipcard as shown in FIG. 6b.

[0026] In another embodiment shown in FIG. 7, a thin and flexible cover720 (e.g. glass with thickness of 0.05 mm) is used first to encapsulatethe device. A flat metal reinforcement 710 is subsequently mounted onthe thin cover.

[0027] While the invention has been particularly shown and describedwith reference to various embodiments, it will be recognized by thoseskilled in the art that modifications and changes may be made to thepresent invention without departing from the spirit and scope thereof.The scope of the invention should therefore be determined not withreference to the above description but with reference to the appendedclaims along with their full scope of equivalents.

What is claimed is:
 1. A device comprising: a substrate including adevice region; and a support lid on the substrate, the lid encapsulatingthe device and reducing the substrate's susceptibility to breakage. 2.The device of claim 1 wherein the device comprises an OLED device. 3.The device of claim 2 wherein the device is integrated into a flexiblesurface.
 4. The device of claim 3 wherein the area occupied by thedisplay comprises a small fraction of the total area of the flexiblesurface.
 5. The device of claim 4 wherein the flexible surface comprisesa chip card.
 6. The device of claim 5 wherein the substrate comprises abrittle material.
 7. The device of claim 6 wherein the substratecomprises transparent material.
 8. The device of claim 7 wherein thesubstrate comprises glass.
 9. The device of claim 7 wherein the supportlid comprises a material more ductile and stiff than the substrate. 10.The device of claim 9 wherein the lid material comprises metal.
 11. Thedevice of claim 10 wherein the lid comprises a thickness of about 0.04mm to 0.4 mm.
 12. The device of claim 11 wherein the substrate comprisesa thickness of less than 0.4 mm.
 13. The device of claim 12 wherein thedevice comprises a thickness of less than 0.6 mm.
 14. The device ofclaim 13 wherein the substrate material comprises glass.
 15. The deviceof claim 14 wherein the lid comprises different shapes.
 16. The deviceof claim 15 wherein the lid comprises a thin and flat shape.
 17. Thedevice of claim 16 wherein the lid comprises a shape that extends theouter dimensions of the substrate.
 18. The device of claim 17 whereinthe lid comprises a round shape.
 19. The device of claim 17 wherein thelid comprises a wedge shape.
 20. The device of claim 15 wherein the lidcomprises a stamped shape, the lid forming a cavity over the substrate.21. The device of claim 20 wherein desiccant material is deposited inthe cavity, absorbing residual moisture and oxygen.
 22. The device ofclaim 1 wherein the device is integrated into a flexible surface. 23.The device of claim 22 wherein the area occupied by the displaycomprises a small fraction of the total area of the flexible surface.24. The device of claim 23 wherein the flexible surface comprises a chipcard.
 25. The device of claim 23 wherein the substrate comprises abrittle material.
 26. The device of claim 25 wherein the support lidcomprises a material more ductile and stiff than the substrate.
 27. Thedevice of claim 26 wherein the device comprises a thickness of less than0.6 mm.
 28. The device of claim 26 wherein the lid comprises differentshapes.
 29. The device of claim 1 wherein the substrate comprises abrittle material.
 30. The device of claim 29 wherein the support lidcomprises a material more ductile and stiff than the substrate.
 31. Thedevice of claim 30 wherein the lid material comprises metal.
 32. Thedevice of claim 31 wherein the device comprises a thickness of less than0.6 mm.
 33. The device of claim 32 wherein the lid comprises differentshapes.
 34. A device comprising: a substrate including a device region;a lid on the substrate, the lid encapsulating the device; and areinforcement layer on the lid, reducing the device's susceptibility tobreakage.
 35. The device of claim 34 wherein the device comprises anOLED device.
 36. The device of claim 35 wherein the device is integratedinto a flexible surface.
 37. The device of claim 36 wherein the areaoccupied by the display comprises a small fraction of the total area ofthe flexible surface.
 38. The device of claim 37 wherein the flexiblesurface comprises a chip card.
 39. The device of claim 37 wherein thesubstrate comprises a brittle material.
 40. The device of claim 39wherein the reinforcement layer comprises a material more ductile andstiff than the substrate.
 41. The device of claim 40 wherein thereinforcement layer comprises different shapes.
 42. The device of claim41 wherein the reinforcement layer comprises a thin and flat shape. 43.The device of claim 42 wherein the reinforcement layer comprises a shapethat extends the outer dimensions of the substrate.
 44. The device ofclaim 43 wherein the reinforcement layer comprises a round shape. 45.The device of claim 43 wherein the reinforcement layer comprises a wedgeshape.
 46. The device of claim 34 wherein the device is integrated intoa flexible surface.
 47. The device of claim 46 wherein the area occupiedby the display comprises a small fraction of the total area of theflexible surface.
 48. The device of claim 47 wherein the flexiblesurface comprises a chip card.
 49. The device of claim 48 wherein thereinforcement layer comprises a material more ductile and stiff than thesubstrate.
 50. A device comprising: a substrate including a deviceregion; isolation pillars formed on the substrate, the pillarssupporting layers above them and isolating cathode materials; and asupport lid on the substrate, the lid encapsulating the device andreducing the substrate's susceptibility to breakage.